Datasheet LT1172, LT1171, LT1170 Datasheet (Linear Technology)

High Efficiency Switching Regulators

INPUT VOLTAGE (V)

0

POWER (W) **

100

80

60

40

20

0

40

LT1170/1/2 TA02

10

20

30

50

* ROUGH GUIDE ONLY. BUCK MODE

P

OUT

= (5A)(V

OUT

) SPECIAL TOPOLOGIES DELIVER MORE POWER.

** DIVIDE VERTICAL POWER SCALE

BY TWO FOR LT1171, BY FOUR

FOR LT1172.

BOOST

BUCK-BOOST V

O

= 30V

FLYBACK

BUCK-BOOST

V

O

= 5V

LT1170

FEATURES

■

Wide Input Voltage Range: 3V to 60V

■

Low Quiescent Current: 6mA

■

I

nternal 5A Switch (2.5A for LT1171,

1.25A for LT1172)

■

Shutdown Mode Draws Only 50µA Supply Current

■

Very Few External Parts Required

■

Self-Protected Against Overloads

■

Operates in Nearly All Switching Topologies

■

Flyback-Regulated Mode Has Fully Floating Outputs

■

Comes in Standard 5-Pin Packages

■

LT1172 Available in 8-Pin MiniDIP and Surface Mount Packages

■

Can Be Externally Synchronized

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APPLICATIO S

■

Logic Supply 5V at 10A

■

5V Logic to ±15V Op Amp Supply

■

Battery Upconverter

■

Power Inverter (+ to –) or (– to +)

■

Fully Floating Multiple Outputs

USER NOTE:

This data sheet is only intended to provide specifications, graphs, and a general functional description of the LT1170/LT1171/LT1172. Application circuits are included to show the capability of the LT1170/LT1171/LT1172. A complete design manual (AN19) should be obtained to assist in developing new designs. This manual contains a comprehensive discussion of both the LT1070 and the external components used with it, as well as complete formulas for calculating the values of these components. The manual can also be used for the LT1170/LT1171/LT1172 by factoring in the higher frequency. A CAD design program called SwitcherCAD

TM

is also available.

LT1170/LT1171/LT1172

100kHz, 5A, 2.5A and 1.25A

U

DESCRIPTIO

The LT®1170/LT1171/LT1172 are monolithic high power switching regulators. They can be operated in all standard switching configurations including buck, boost, flyback, forward, inverting and “Cuk.” A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry. Integration of all functions allows the LT1170/LT1171/LT1172 to be built in a standard 5-pin TO-3 or TO-220 power package as well as the 8-pin packages (LT1172). This makes them extremely easy to use and provides “bust proof” operation similar to that obtained with 3-pin linear regulators.

The LT1170/LT1171/LT1172 operate with supply voltages from 3V to 60V, and draw only 6mA quiescent current. They can deliver load power up to 100W with no external power devices. By utilizing current-mode switching techniques, they provide excellent AC and DC load and line regulation.

The LT1170/LT1171/LT1172 have many unique features not found even on the vastly more difficult to use low power control chips presently available. They use adaptive antisat switch drive to allow very wide ranging load currents with no loss in efficiency. An externally activated shutdown mode reduces total supply current to 50µA typically for standby operation.

, LTC and LT are registered trademarks of Linear Technology Corporation.

SwitcherCAD is a trademark of Linear Technology Corporation.

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TYPICAL APPLICATIO

Boost Converter (5V to 12V)

L1**

5V

50µH

V

IN

V

GND

LT1170

V

C

R3 1k

+

C3* 100µF

*REQUIRED IF INPUT LEADS ≥ 2"

MBR330

SW

FB

C1 1µF

** COILTRONICS 50-2-52 PULSE ENGINEERING 92114

L2

OUTPUT

10µH

FILTER

C3

100µF

D1

12V

R1

10.7k 1%

R2

1.24k 1%

1170/1/2 TA01

1A

+

C2 1000µF

Maximum Output Power*

1

LT1170/LT1171/LT1172

2

4

1

3

V

SW

V

C

FB

CASE IS GND

V

IN

K PACKAGE

4-LEAD TO-3 METAL CAN

BOTTOM VIEW

WWWU

ABSOLUTE AXI U RATI GS

(Note 1)

Supply Voltage

LT1170/71/72HV (Note 2) .................................. 60V

LT1170/71/72 (Note 2)....................................... 40V

Switch Output Voltage

LT1170/71/72HV ................................................ 75V

LT1170/71/72..................................................... 65V

LT1172S8........................................................... 60V

Feedback Pin Voltage (Transient, 1ms) ................ ±15V

Storage Temperature Range ............... –65°C to 150°C

Lead Temperature (Soldering, 10 sec)................. 300°C

UU

W

PACKAGE/ORDER I FOR ATIO

TOP VIEW

GND

1

V

2

C

FB

3

NC*

4

J8 PACKAGE

8-LEAD CERDIP

S8 PACKAGE

8-LEAD PLASTIC SO

* Do not connect Pin 4 of the LT1172 DIP or SO to external

circuitry. This pin may be active in future revisions.

T

= 150°C, θJA = 100°C/W (J)

JMAX

= 100°C, θJA = 100°C/W (N)

T

JMAX

T

= 100°C, θJA = 120°C/W to 150°C/W

JMAX

depending on board layout (S)

E2

8

V

7

SW

E1

6

V

5

IN

N8 PACKAGE 8-LEAD PDIP

ORDER PART

NUMBER

LT1172MJ8 LT1172CJ8 LT1172CN8 LT1172IN8 LT1172CS8 LT1172IS8

S8 PART MARKING

1172

1172I

Operating Junction Temperature Range

LT1170/71/72M......................... –55°C to 150°C

LT1170/71/72HVC,

LT1170/71/72C (Oper.) .............. 0°C to 100°C

LT1170/71/72HVC

LT1170/71/72C (Sh. Ckt.) .......... 0°C to 125°C

LT1170/71/72HVI,

LT1170/71/72I (Oper.) .......... –40°C to 100°C

LT1170/71/72HVI,

LT1170/71/72I (Sh. Ckt.) ...... –40°C to 125°C

TOP VIEW

1

NC

2

NC

3

GND

4

V

C

5

FB

6

NC

7

NC

8

NC

SW PACKAGE

16-LEAD PLASTIC SO WIDE

T

= 100°C, θJA = 150°C/W

JMAX

Based on continuous operation.

= 125°C for intermittent fault conditions.

T

JMAX

16 15 14 13 12 11 10

9

NC NC E2 V

SW

E1 V

IN

NC NC

ORDER PART

NUMBER

LT1172CSW

C

I

T

*θ will vary from approximately 25°C/W with 2.8

V

IN

sq. in. of 1oz.

V

SW

copper to 45°C/W

GND

with 0.20 sq. in. of

FB

1oz. copper.

V

C

Somewhat lower values can be obtained with additional copper layers in multilayer boards.

JMAXθJC

LT1170MK 150°C2°C/W 35°C/W LT1170CK 100°C2°C/W 35°C/W LT1171MK 150°C4°C/W 35°C/W LT1171CK 100°C4°C/W 35°C/W LT1172MK 150°C8°C/W 35°C/W LT1172CK 150°C8°C/W 35°C/W

Based on continuous operation.

= 125°C for intermittent fault conditions.

T

JMAX

FRONT VIEW

5 4 3 2 1

Q PACKAGE

5-LEAD DD

T

= 100°C, θJA = *°C/W

JMAX

2

ORDER PART

θ

JA

ORDER PART

NUMBER

LT1170CQ LT1170IQ LT1171CQ LT1171IQ

NUMBER

LT1170MK LT1170CK LT1171MK LT1171CK LT1172MK LT1172CK

LT1171HVCQ LT1172CQ LT1172HVIQ

FRONT VIEW

5 4 3 2 1

T PACKAGE

5-LEAD PLASTIC TO-220

T

LT1170CT/LT1170HVCT 100°C2°C/W 75°C/W LT1171CT/LT1171HVCT 100°C4°C/W 75°C/W LT1172CT/LT1172HVCT 100°C8°C/W 75°C/W

Based on continuous operation.

= 125°C for intermittent fault conditions.

T

JMAX

JMAXθJC

V V GND FB V

IN SW

C

θ

JA

ORDER PART

NUMBER

LT1170CT LT1170IT LT1170HVCT LT1170HVIT LT1171CT LT1171IT LT1171HVCT LT1172CT LT1172HVCT

LT1170/LT1171/LT1172

ELECTRICAL CHARACTERISTICS

perature range, otherwise specifications are at TA = 25°C. VIN = 15V, VC = 0.5V, VFB = V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

REF

I

B

g

m

A

V

I

Q

V

FB

BV Output Switch Breakdown 3V ≤ VIN ≤ V

V

SAT

I

LIM

Reference Voltage Measured at Feedback Pin 1.224 1.244 1.264 V

VC = 0.8V ● 1.214 1.244 1.274 V

Feedback Input Current VFB = V

Error Amplifier ∆IC = ±25µA 3000 4400 6000 µmho Transconductance ● 2400 7000 µmho

Error Amplifier Source or VC = 1.5V 150 200 350 µA Sink Current ● 120 400 µA

Error Amplifier Clamp Hi Clamp, VFB = 1V 1.80 2.30 V Voltage Lo Clamp, VFB = 1.5V 0.25 0.38 0.52 V

Reference Voltage Line 3V ≤ VIN ≤ V Regulation VC = 0.8V

Error Amplifier Voltage Gain 0.9V ≤ VC ≤ 1.4V 500 800 V/V Minimum Input Voltage (Note 5) ● 2.6 3.0 V Supply Current 3V ≤ VIN ≤ V Control Pin Threshold Duty Cycle = 0 0.8 0.9 1.08 V

Normal/Flyback Threshold 0.4 0.45 0.54 V on Feedback Pin

Flyback Reference Voltage IFB = 50µA 15.0 16.3 17.6 V (Note 5) ● 14.0 18.0 V

Change in Flyback Reference 0.05 ≤ IFB ≤ 1mA 4.5 6.8 9 V Voltage

Flyback Reference Voltage IFB = 50µA 0.01 0.03 %/V Line Regulation (Note 5) 7V ≤ VIN ≤ V

Flyback Amplifier ∆IC = ±10µA 150 300 650 µmho Transconductance (gm)

Flyback Amplifier Source VC = 0.6V Source ● 15 32 70 µA and Sink Current IFB = 50µASink ● 25 40 70 µA

Voltage I

Output Switch LT1170 ● 0.15 0.24 Ω “On” Resistance (Note 3) LT1171

Control Voltage to Switch LT1170 8 A/V Current Transconductance LT1171 4 A/V

Switch Current Limit (LT1170) Duty Cycle = 50% TJ ≥ 25°C ● 510A

(LT1171) Duty Cycle = 50% TJ ≥ 25°C ● 2.5 5.0 A

(LT1172) Duty Cycle = 50% TJ ≥ 25°C ● 1.25 3.0 A

REF

= 1.5mA LT1170HV/LT1171HV/LT1172HV ● 75 90 V

SW

LT1172 ● 0.60 1.00 Ω

LT1172 2 A/V

Duty Cycle = 50% T Duty Cycle = 80% (Note 4) ● 410A

Duty Cycle = 50% T Duty Cycle = 80% (Note 4) ● 2.0 5.0 A

Duty Cycle = 50% T Duty Cycle = 80% (Note 4) ● 1.00 2.5 A

The ● denotes the specifications which apply over the full operating tem-

, output pin open, unless otherwise noted.

REF

350 750 nA

● 1100 nA

MAX

, VC = 0.6V 6 9 mA

MAX

, LT1170/LT1171/LT1172 ● 65 90 V

MAX

LT1172S8 ● 60 80 V

< 25°C ● 511A

J

< 25°C ● 2.5 5.5 A

J

< 25°C ● 1.25 3.5 A

J

● 0.03 %/V

● 0.6 1.25 V

● 0.30 0.50 Ω

3

LT1170/LT1171/LT1172

ELECTRICAL CHARACTERISTICS

perature range, otherwise specifications are at TA = 25°C. VIN = 15V, VC = 0.5V, VFB = V

The ● denotes the specifications which apply over the full operating tem-

, output pin open, unless otherwise noted.

REF

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

∆I

IN

∆I

SW

Supply Current Increase 25 35 mA/A During Switch On-Time

f Switching Frequency 88 100 112 kHz

● 85 115 kHz

DC

Maximum Switch Duty Cycle ● 85 92 97 %

MAX

Shutdown Mode 3V ≤ VIN ≤ V Supply Current V

= 0.05V

C

Shutdown Mode 3V ≤ VIN ≤ V Threshold Voltage

MAX

100 150 250 mV

● 50 300 mV

100 250 µA

Flyback Sense Delay Time (Note 5) 1.5 µs

Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired.

Note 2: Minimum effective switch “on” time for the LT1170/71/72 (in current limit only) is ≈ 0.6µs. This limits the maximum safe input voltage during an output shorted condition. Buck mode and inverting mode input voltage during an output shorted condition is limited to:

(max, output shorted) = 15V +

V

IN

buck and inverting mode

(R)(IL) + Vf

(t)(f)

R = Inductor DC resistance IL = 10A for LT1170, 5A for LT1171, and 2.5A for LT1172 Vf = Output catch diode forward voltage at I

L

t = 0.6µs, f = 100kHz switching frequency Maximum input voltage can be increased by increasing R or Vf.

Transformer designs will tolerate much higher input voltages because leakage inductance limits rate of rise of current in the switch. These designs must be evaluated individually to assure that current limit is well controlled up to maximum input voltage.

Boost mode designs are never protected against output shorts because the external catch diode and inductor connect input to output.

Note 3: Measured with V

in hi clamp, VFB = 0.8V. ISW = 4A for LT1170,

C

2A for LT1171, and 1A for LT1172. Note 4: For duty cycles (DC) between 50% and 80%, minimum

guaranteed switch current is given by I

= 1.67 (2 – DC) for the LT1171, and I

I

LIM

= 3.33 (2 – DC) for the LT1170,

LIM

= 0.833 (2 – DC) for the

LIM

LT1172. Note 5: Minimum input voltage for isolated flyback mode is 7V. V

MAX

=

55V for HV grade in fully isolated mode to avoid switch breakdown.

External current limiting such as that shown in AN19, Figure 39, will provide protection up to the full supply voltage rating. C1 in Figure 39 should be reduced to 200pF.

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Switch Current Limit vs Duty Cycle*

16

12

8

SWITCH CURRENT (A)

4

0

–55°C

125°C

* DIVIDE VERTICAL SCALE BY TWO FOR LT1171, BY FOUR FOR LT1172.

0

30

10

20

25°C

40

50

607080 90 100

DUTY CYCLE (%)

1170/1/2 G01

Minimum Input Voltage Switch Saturation Voltage

2.9

2.8

2.7

2.6

2.5

MINIMUM INPUT VOLTAGE (V)

2.4

2.3 –50 0

–75

SWITCH CURRENT = I

SWITCH CURRENT = 0A

–25

25

TEMPERATURE (°C)

50 150

MAX

100

75

4

125

1170/1/2 G02

1.6

1.4

1.2

1.0

0.8

0.6

0.4

SWITCH SATURATION VOLTAGE (V)

0.2

0

* DIVIDE CURRENT BY TWO FOR LT1171, BY FOUR FOR LT1172.

2

1

SWITCH CURRENT (A)*

4567

3

150°C

100°C

25°C

–55°C

8

1170/1/2 G03

INPUT VOLTAGE (V)

0

SUPPLY CURRENT (mA)

10

20

30 40

1170/1/2 G09

50

15 14 13 12 11 10

9 8 7 6 5

60

TJ = 25°C

NOTE THAT THIS CURRENT DOES NOT INCLUDE DRIVER CURRENT, WHICH IS A FUNCTION OF LOAD CURRENT AND DUTY CYCLE.

90% DUTY CYCLE

50% DUTY CYCLE

10% DUTY CYCLE

0% DUTY CYCLE

* UNDER VERY LOW OUTPUT CURRENT CONDITIONS, DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH 10% OR LESS.

VC PIN VOLTAGE (V)

300

200

100

0

–100

–200

–300

–400

1170/1/2 G12

V

C

PIN CURRENT (µA)

0 2.0

0.5

1.0

1.5

2.5

VFB = 1.5V (CURRENT INTO VC PIN)

VFB = 0.8V (CURRENT OUT OF VC PIN)

TJ = 25°C

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Line Regulation

5 4 3 2 1 0

TJ = –55°C

–1 –2 –3

REFERENCE VOLTAGE CHANGE (mV)

–4 –5

10

0

20

INPUT VOLTAGE (V)

TJ = 150°C

30 40

Supply Current vs Supply Voltage (Shutdown Mode)

160

TJ = 25°C

140

120

100

80

60

SUPPLY CURRENT (µA)

40

20

0

10 20

VC = 50mV

VC = 0V

30

SUPPLY VOLTAGE (V)

40

TJ = 25°C

50

1170/1/2 G04

50

1170/1/2 G07

60

Reference Voltage vs Temperature

1.250

1.248

1.246

1.244

1.242

1.240

1.238

REFERENCE VOLTAGE (V)

1.236

1.234 –75 –25

–50 0

TEMPERATURE (°C)

25

100

50 150

75

Driver Current* vs Switch Current

160

140

120

100

80

60

DRIVER CURRENT (mA)

40

20

0

123

* AVERAGE LT1170 POWER SUPPLY CURRENT IS FOUND BY MULTIPLYING DRIVER CURRENT BY DUTY CYCLE, THEN ADDING QUIESCENT CURRENT.

TJ = –55°C

TJ = ≥ 25°C

4

SWITCH CURRENT (A)

125

1170/1/2 G05

1170/1/2 G08

LT1170/LT1171/LT1172

Feedback Bias Current vs Temperature

800

700

600

500

400

300

200

FEEDBACK BIAS CURRENT (nA)

100

0

–50 0

–75 –25

TEMPERATURE (°C)

Supply Current vs Input Voltage*

5

50 150

25

100

125

75

1170/1/2 G06

Shutdown Mode Supply Current

200 180 160 140 120 100

80 60

SUPPLY CURRENT (µA)

40 20

0

10

0

TJ = 150°C

30

40

20

VC PIN VOLTAGE (mV)

–55°C ≤ TJ ≤ 125°C

607080

50

Error Amplifier Transconductance VC Pin Characteristics

5000 4500 4000 3500 3000 2500 2000 1500 1000

TRANSCONDUCTANCE (µmho)

500

0

–50 0

90 100

1170/1/2 G10

–75 –25

TEMPERATURE (°C)

gm =

50 150

25

∆I (V

∆V (FB PIN)

100

75

PIN)

C

125

1170/1/2 G11

5

LT1170/LT1171/LT1172

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Idle Supply Current vs Temperature

11

VC = 0.6V

10

9 8 7 6 5 4

IDLE SUPPLY CURRENT (mA)

3 2 1

–50 0

–75 –25

400

350

300

250

200

150

PIN VOLTAGE (mV)

C

V

100

50

0

–50 0

–75 –25

V

SUPPLY

V

SUPPLY

TEMPERATURE (°C)

CURRENT (OUT OF VC PIN)

VOLTAGE

VC VOLTAGE IS REDUCED UNTIL REGULATOR CURRENT DROPS BELOW 300µA

TEMPERATURE (°C)

= 60V

= 3V

100

50 150

75

25

100

50 150

75

25

125

1170/1/2 G13

125

1170/1/2 G16

500 450 400 350 300 250 200 150

FEEDBACK VOLTAGE (mV)

100

50

0

–400

–350

V

–300

C

PIN CURRENT (µA)

–250

–200

–150

–100

–50

0

TIME (µs)

Feedback Pin Clamp Voltage Switch “Off” Characteristics

1000

900 800

SUPPLY

= 15V

40

V

50

SUPPLY

= 40V

V = 55V

607080

SUPPLY

700

= 3V

10

30

20

SWITCH VOLTAGE (V)

V

600

V

500

SUPPLY

400 300

SWITCH CURRENT (µA)

200 100

0

0.1

0

0.3

0.2 FEEDBACK CURRENT (mA)

0.4

–55°C

25°C

150°C

0.5

0.6

0.7

0.8

0.9 1.0

1170/1/2 G14

Isolated Mode Flyback Reference Voltage

23

22

21

20

19

18

FLYBACK VOLTAGE (V)

17

16

15

–50 0

–75 –25

TEMPERATURE (°C)

RFB = 500Ω

RFB = 1k

RFB = 10k

50 150

75

25

100

2.2

2.0

1.8

1.6

1.4

1.2

1.0

Flyback Blanking TimeShutdown Thresholds

–50 0

–75

–25

JUNCTION TEMPERATURE (°C)

100

50 150

75

25

125

1170/1/2 G17

90 100

1170/1/2 G15

125

1170/1/2 G18

6

Transconductance of Error Amplifier

7000

6000

5000

4000

3000

2000

1000

TRANSCONDUCTANCE (µmho)

0

–1000

1k

10k 100k

FREQUENCY (Hz)

θ

g

m

1M 10M

1170/1/2 G19

–30

0

30

PHASE (DEG)

60

90

120

150

180

210

Normal/Flyback Mode Threshold on Feedback Pin

500 490 480 470 460 450 440 430 420

FEEDBACK PIN VOLTAGE (mV)

410 400

FEEDBACK PIN VOLTAGE

(AT THRESHOLD)

FEEDBACK PIN CURRENT

–50

–25 25

0

(AT THRESHOLD)

50

TEMPERATURE (°C)

75

100

125

1170/1/2 G20

150

–24 –22 –20 –18 –16 –14 –12 –10 –8 –6 –4

FEEDBACK PIN CURRENT (µA)

BLOCK DIAGRA

LT1170/LT1171/LT1172

W

V

IN

2.3V REG

100kHz

OSC

MODE

SELECT

FB

1.24V REF

–

ERROR

AMP

+

LOGIC DRIVER

COMP

V

SHUTDOWN CIRCUIT

0.15V

FLYBACK

ERROR

AMP

C

(LT1170 AND LT1171 ONLY)

ANTI-

SAT

CURRENT

AMP

≈

GAIN 6

16V

+

–

5A, 75V

SWITCH

OUT

0.02 (0.04 (0.16

LT1172

Ω

Ω LT1171) Ω LT1172)

0.16Ω

†

ALWAYS CONNECT E1 TO THE GROUND PIN ON MINIDIP, 8- AND 16-PIN SURFACE MOUNT PACKAGES. E1 AND E2 INTERNALLY TIED TO GROUND ON TO-3 AND TO-220 PACKAGES.

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OPERATIO

The LT1170/LT1171/LT1172 are current mode switchers. This means that switch duty cycle is directly controlled by switch current rather than by output voltage. Referring to the block diagram, the switch is turned “on” at the start of each oscillator cycle. It is turned “off” when switch current reaches a predetermined level. Control of output voltage is obtained by using the output of a voltage sensing error amplifier to set current trip level. This technique has several advantages. First, it has immediate response to input voltage variations, unlike ordinary switchers which have notoriously poor line transient response. Second, it reduces the 90° phase shift at midfrequencies in the energy storage inductor. This greatly simplifies closedloop frequency compensation under widely varying input voltage or output load conditions. Finally, it allows simple pulse-by-pulse current limiting to provide maximum switch

†

E1

E2

1170/1/2 BD

protection under output overload or short conditions. A low dropout internal regulator provides a 2.3V supply for all internal circuitry on the LT1170/LT1171/LT1172. This low dropout design allows input voltage to vary from 3V to 60V with virtually no change in device performance. A 100kHz oscillator is the basic clock for all internal timing. It turns “on” the output switch via the logic and driver circuitry. Special adaptive anti-sat circuitry detects onset of saturation in the power switch and adjusts driver current instantaneously to limit switch saturation. This minimizes driver dissipation and provides very rapid turnoff of the switch.

A 1.2V bandgap reference biases the positive input of the error amplifier. The negative input is brought out for output voltage sensing. This feedback pin has a second

7

LT1170/LT1171/LT1172

U

OPERATIO

function; when pulled low with an external resistor, it programs the LT1170/LT1171/LT1172 to disconnect the main error amplifier output and connects the output of the flyback amplifier to the comparator input. The LT1170/ LT1171/LT1172 will then regulate the value of the flyback pulse with respect to the supply voltage.* This flyback pulse is directly proportional to output voltage in the traditional transformer coupled flyback topology regulator. By regulating the amplitude of the flyback pulse, the output voltage can be regulated with no direct connection between input and output. The output is fully floating up to the breakdown voltage of the transformer windings. Multiple floating outputs are easily obtained with additional windings. A special delay network inside the LT1170/ LT1171/LT1172 ignores the leakage inductance spike at the leading edge of the flyback pulse to improve output regulation.

The error signal developed at the comparator input is brought out externally. This pin (VC) has four different functions. It is used for frequency compensation, current limit adjustment, soft starting, and total regulator shutdown. During normal regulator operation this pin sits at a voltage between 0.9V (low output current) and 2.0V (high output current). The error amplifiers are current output (gm) types, so this voltage can be externally clamped for adjusting current limit. Likewise, a capacitor coupled external clamp will provide soft start. Switch duty cycle goes to zero if the VC pin is pulled to ground through a diode, placing the LT1170/LT1171/LT1172 in an idle mode. Pulling the VC pin below 0.15V causes total regulator shutdown, with only 50µA supply current for shutdown circuitry biasing. See AN19 for full application details.

Extra Pins on the MiniDIP and Surface Mount Packages

The 8- and 16-pin versions of the LT1172 have the emitters of the power transistor brought out separately from the ground pin. This eliminates errors due to ground pin voltage drops and allows the user to reduce switch current limit 2:1 by leaving the second emitter (E2) disconnected. The first emitter (E1) should always be connected to the ground pin. Note that switch “on” resistance doubles when E2 is left open, so efficiency will suffer somewhat

when switch currents exceed 300mA. Also, note that chip dissipation will actually normal load operation, even though dissipation in current limit mode will next.

Thermal Considerations When Using the MiniDIP and SW Packages

The low supply current and high switch efficiency of the LT1172 allow it to be used without a heat sink in most applications when the TO-220 or TO-3 package is selected. These packages are rated at 50°C/W and 35°C/W respectively. The miniDIPs, however, are rated at 100°C/W in ceramic (J) and 130°C/W in plastic (N).

Care should be taken for miniDIP applications to ensure that the worst case input voltage and load current conditions do not cause excessive die temperatures. The following formulas can be used as a rough guide to calculate LT1172 power dissipation. For more details, the reader is referred to Application Note 19 (AN19), “Efficiency Calculations” section.

Average supply current (including driver current) is:

IIN ≈ 6mA + ISW(0.004 + DC/40) ISW = switch current

DC = switch duty cycle

Switch power dissipation is given by:

PSW = (ISW)2 • (RSW)(DC) RSW = LT1172 switch “on” resistance (1Ω maximum)

Total power dissipation is the sum of supply current times input voltage plus switch power:

P

D(TOT)

In a typical example, using a boost converter to generate 12V at 0.12A from a 5V input, duty cycle is approximately 60%, and switch current is about 0.65A, yielding:

IIN = 6mA + 0.65(0.004 + DC/40) = 18mA PSW = (0.65)2 • (1Ω)(0.6) = 0.25W P

D(TOT)

decrease

= (IIN)(VIN) + P

= (5V)(0.018A) + 0.25 = 0.34W

increase

. See “Thermal Considerations”

SW

with E2 open during

*See note under block diagram.

8

OPERATIO

LT1170/LT1171/LT1172

U

Temperature rise in a plastic miniDIP would be 130°C/W times 0.34W, or approximately 44°C. The maximum ambient temperature would be limited to 100°C (commercial temperature limit) minus 44°C, or 56°C.

In most applications, full load current is used to calculate die temperature. However, if overload conditions must also be accounted for, four approaches are possible. First, if loss of regulated output is acceptable under overload conditions, the internal

thermal limit

of the LT1172 will protect the die in most applications by shutting off switch current.

Thermal limit is not a tested parameter

, however, and should be considered only for noncritical applications with temporary overloads. A second approach is to use the larger TO-220 (T) or TO-3 (K) package which, even without a heat sink, may limit die temperatures to safe levels under overload conditions. In critical situations, heat sinking of these packages is required; especially if overload conditions must be tolerated for extended periods of time.

The third approach for lower current applications is to leave the second switch emitter (miniDIP only) open. This increases switch “on” resistance by 2:1, but reduces switch current limit by 2:1 also, resulting in a net 2:1 reduction in I2R switch dissipation under current limit conditions.

The fourth approach is to clamp the VC pin to a voltage less than its internal clamp level of 2V. The LT1172 switch current limit is zero at approximately 1V on the VC pin and 2A at 2V on the VC pin. Peak switch current can be externally clamped between these two levels with a diode. See AN19 for details.

Synchronizing with Bipolar Transistor

LT1170/LT1171/LT1172 Synchronizing

The LT1170/LT1171/LT1172 can be externally synchronized in the frequency range of 120kHz to 160kHz. This is accomplished as shown in the accompanying figures. Synchronizing occurs when the VC pin is pulled to ground with an external transistor. To avoid disturbing the DC characteristics of the internal error amplifier, the width of the synchronizing pulse should be under 0.3µs. C2 sets the pulse width at ≅ 0.2µs. The effect of a synchronizing pulse on the LT1170/LT1171/LT1172 amplifier offset can be calculated from:



KT



q

∆V

KT



=

OS

= 26mV at 25°C



()()







tfI

SSC





I

C



V

C

+



R

3



q tS= pulse width fS= pulse frequency IC=VC source current (≈200µA) VC= operating VC voltage (1V to 2V) R3 = resistor used to set mid-frequency “zero” in frequency compensation network.

With tS = 0.2µs, fS = 150kHz, VC = 1.5V, and R3 = 2k, offset voltage shift is ≈3.8mV. This is not particularly bothersome, but note that high offsets could result if R3 were reduced to a much lower value. Also, the synchronizing transistor must sink higher currents with low values of R3, so larger drives may have to be used. The transistor must be capable of pulling the VC pin to within 200mV of ground to ensure synchronizing.

Synchronizing with MOS Transistor

V

GND

IN

LT1170

V

IN

LT1170

V

C

C2

R1

39pF

R2

2.2k

3k

FROM 5V

LOGIC

1170/1/2 OP01

R3

2N2369

C1

GND

V

C

R3

VN2222*

C1

* SILICONIX OR EQUIVALENT

1N4158

R2

2.2k

D1

C2

100pF

D2 1N4158

FROM 5V

LOGIC

1170/1/2 OP02

9

LT1170/LT1171/LT1172

TYPICAL APPLICATIO S

U

Flyback Converter

C4*

100µF

V

20V TO 30V

+

IN

V

IN

LT1170

GND

*REQUIRED IF INPUT LEADS ≥ 2"

V

C

V

SW

FB

R3

1.5k C2

0.15µF

D3 25V 1W

D2 MUR110

N* = 1/3

1

b

V

OUT

d

I

PRI

I

PRI

(I

)(LL)

PRI

V

SNUB

CLAMP TURN-ON

SPIKE

PRIMARY FLYBACK VOLTAGE = LT1170 SWITCH VOLTAGE

AREA “a” = AREA “b” TO MAINTAIN ZERO DC VOLTS ACROSS PRIMARY

+ V

f

SECONDARY VOLTAGE

N • V

IN

AREA “c” = AREA “d” TO MAINTAIN ZERO DC VOLTS ACROSS SECONDARY

PRIMARY CURRENT

I

/N

PRI

SECONDARY CURRENT

LT1170 SWITCH CURRENT

SNUBBER DIODE CURRENT

V

OUT

1170/1/2 TA03

+ Vf

N

OPTIONAL

L2

FILTER

5µH

C4

100µF

D1

N*

+

C1 2000µF

V 5V 6A

R1

3.74k

R2

1.24k

OUT

V

SNUB

V

a

IN

0V

c

∆I

0

I

PRI

0

t =

LCD Contrast Supply

5V*

V

IN

V

TO 400mV

V

SW

FB

C

C4

0.047µF

WITH C2 = 2µF TANTALUM. IF LOWER RIPPLE IS DESIRED, INCREASE C2, OR ADD

P-P

E2

LT1172

E1

GND

OPTIONAL

SHUTDOWN

D2, D3 = ER82.004 600mA SCHOTTKY. OTHER FAST SWITCHING TYPES MAY BE USED.

*

VIN AND BATTERY MAY BE TIED TOGETHER. MAXIMUM VALUE FOR V BATTERY VOLTAGES, HIGHEST EFFICIENCY IS OBTAINED BY RUNNING THE LT1172 V WILL AUTOMATICALLY TURN OFF THE LT1172. EFFICIENCY IS ABOUT 80% AT I

R1, R2, R3 ARE MADE LARGE TO MINIMIZE BATTERY DRAIN IN SHUTDOWN, WHICH IS APPROXIMATELY V

**

FOR HIGH EFFICIENCY, L1 SHOULD BE MADE ON A FERRITE OR MOLYPERMALLOY CORE. PEAK INDUCTOR CURRENTS ARE ABOUT 600mA AT P

OUTPUT RIPPLE IS ABOUT 200mV

***

A 10Ω , 1µF TANTALUM OUTPUT FILTER.

VN2222

= 0.7Ω. INDUCTOR SERIES RESISTANCE SHOULD BE LESS THAN 0.4Ω FOR HIGH EFFICIENCY.

OUT

P-P

R3 15k

L1**

50µH

V

*

BAT

3V TO 20V

+

D1

R2

100k

R1

200k

IS EQUAL TO THE NEGATIVE OUTPUT + 1V. WITH HIGHER

BAT

1N914

C3

0.0047µF

PIN FROM 5V. SHUTTING OFF THE 5V SUPPLY

IN

= 25mA.

OUT

C1 1µF TANTALUM

D2

D3

/(R1 + R2 + R3).

BAT

V

OUT

–10V TO –26V

C2*** 2µF

+

TANTALUM

1170/1/2 TA04

10

TYPICAL APPLICATIO S

LT1170/LT1171/LT1172

U

(Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.)

Driving High Voltage FET

(for Off-Line Applications, See AN25)

G

D1

1170/1/2 TA05

10V TO

20V

V

IN

V

SW

+

LT1170

GND

Negative-to-Positive Buck-Boost Converter

L1**

50µH

V

IN

V

SW

+

C4*

100µF

OPTIONAL

INPUT FILTER

L3

V

IN

–20V

REQUIRED IF INPUT LEADS ≥ 2"

*

PULSE ENGINEERING 92114, COILTRONICS 50-2-52

**

†

THIS CIRCUIT IS OFTEN USED TO CONVERT –48V TO 5V. TO GUARANTEE FULL SHORT-CIRCUIT PROTECTION, THE CURRENT LIMIT CIRCUIT SHOWN IN AN19, FIGURE 39, SHOULD BE ADDED WITH C1 REDUCED TO 200pF.

GND

LT1170

FB

V

C

R3

2.2k C1

0.22µF

D1

R2

1.24k

D

Q1

†

L2

OPTIONAL

OUTPUT

FILTER

+

C2 1000µF

Q1

C3

R1

11.3k

1170/1/2 TA07

V 12V 2A

OUT

V

X

R2

≈

R1

500Ω

+

V

IN

–

Q1

NOTE THAT THE LT1170 GND PIN IS NO LONGER COMMON TO V

External Current Limit

LT1170

2V

GND

D1

External Current Limit

LT1170

GND

R1 1k

C1 1000pF

R

S

–

.

IN

V

C

1170/1/2 TA06

V

IN

V

SW

FB

V

C

R2

C2

1170/1/2 TA08

REQUIRED IF INPUT LEADS ≥ 2"

*

PULSE ENGINEERING 92114

**

COILTRONICS 50-2-52

INPUT FILTER

OPTIONAL

L3

–20V

Negative Buck Converter

+

D1

R2

1.24k

L1**

50µH

V

IN

V

+

C3*

100µF

V

IN

LT1170

GND

SW

FB

V

C

C1

R3

C2 1000µF

2N3906

R4

12k

OPTIONAL

OUTPUT

FILTER

LOAD

4µH

L2

–5.2V

4.5A

+

1170/1/2 TA09

C4 200µF

R1

4.64k

Q1

11

LT1170/LT1171/LT1172

TYPICAL APPLICATIO S

†

D3

1N4001

1µF

+

C4

GND

V

IN

LT1170

470Ω, 1W

V

U

Positive-to-Negative Buck-Boost Converter

†

R5

+

V

SW

R1

FB

C

R3 5k

C2

0.1

10.7k

+ +

R2

1.24k

µF

L1**

50µH

High Efficiency Constant Current Charger

C5 100µF*

D2

1N914

C3 2µF

V

IN

10V TO 30V

47Ω

D1

**

R4

C1

1000µF

REQUIRED IF INPUT LEADS ≥ 2"

*

PULSE ENGINEERING 92114, COILTRONICS 50-2-52

†

TO AVOID STARTUP PROBLEMS FOR INPUT VOLTAGES BELOW 10V, CONNECT ANODE OF D3 TO V REMOVE R5. C1 MAY BE REDUCED FOR LOWER OUTPUT CURRENTS. C1 ≈ (500µF)(I FOR 5V OUTPUTS, REDUCE R3 TO 1.5k, INCREASE C2 TO

0.3µF, AND REDUCE R6 TO 100Ω.

†

R6 470

Ω

V

OUT

–12V 2A

OUT

).

, AND

IN

1170/1/2 TA10

INPUT VOLTAGE

+ 2V < 35V

> V

BAT

INPUT VOLTAGE

4.5V TO 20V

+ +

C1

200µF

35V

SHUTDOWN = 5V

†

+

10µF

TANT

1N5819

2.2µF

35V

TANTALUM

RUN = 0V

R3

+

V

LT1006

–

V

25k

–

+

R5

0.05Ω

R4 1k

100µH, 1A

V

SW

D1

C2

R6

78k

LT1171

V

IN

GND

2N3904

R8

R7

1k

22k

FB

V

C

+

C3

0.47µF

D2 MBR340

R2

1k

C4

0.01µF

1.244V • R4

I =

CHRG

* L2 REDUCES RIPPLE CURRENT INTO THE BATTERY BY ABOUT 20:1. IT MAY BE OMITTED IF DESIRED.

L1

R3 • R5

+

L2*

10µH, 1A

C4 200µF 25V

= 1A AS SHOWN

1A

+

BATTERY 2V TO 25V

1170/1/2 TA11

Backlight CCFL Supply (see AN45 for details)

L2***

1k

1N5818

V

IN

2µF

V

SW

FB

V

C

+

E2

LT1172

E1

GND

1 F

L1**

300µH

Q1,Q2 = BCP56 OR MPS650/561

C6

µ

*

COILTRONICS CTX300-4

**

SUMIDA 6345-020 OR COILTRONICS 110092-1

***

†

A MODIFICATION WILL ALLOW OPERATION DOWN TO 4.5V. CONSULT FACTORY.

A

Q1*

0.02µF

Q2*

B

D1

1N914

33pF

3kV

R3

10k

LAMP

D2 1N914

R1

560Ω

50k

INTENSITY

ADJUST

1170/1/2 TA12

12

TYPICAL APPLICATIO S

V

IN

2.2µF

+

C5* 100µF

D3

+

C3

U

GND

Positive Buck Converter

V

IN

V

SW

LT1170

FB

V

C

R3 470Ω

C1 1µF

r

D1

Negative Boost Regulator

REQUIRED IF INPUT LEADS ≥ 2"

*

PULSE ENGINEERING 92114

**

COILTRONICS 50-2-52

R2

1.24k

R1

3.74k

1N914

+

C2 1µF

LT1170/LT1171/LT1172

L2

4µH

C5 200µF

R4 10Ω

5V, 4.5A

100mA MINIMUM

1170/1/2 TA13

D2

L1**

50µH

1000µF

OPTIONAL

OUTPUT

FILTER

+

C4

+

C4*

470µF

L1

V

–15V

IN

50µH

REQUIRED IF INPUT LEADS ≥ 2"

*

D2

V

SW

GND

IN

LT1170

R1 27k

+ +

C3 10µF

FB

V

C

R3

3.3k C2

0.22µF

R2

1.24k

D1

C1 1000µF

V

OUT

–28V, 1A

R

O

(MINIMUM LOAD)

1170/1/2 TA14

V

Driving High Voltage NPN

C1

D2

V

IN

LT1170

GND

R2**

V

SW

R1*

D1

SETS IB (ON)

*

SETS I

**

B

Q1

(OFF)

1170/1/2 TA15

13

LT1170/LT1171/LT1172

TYPICAL APPLICATIO S

U

Forward Converter

V

IN

20V TO 30V

V

IN

+

C1 330µF 35V

<0.3V = NORMAL MODE >2.5V = SHUTDOWN OPEN = BURST MODE

GND

C6

0.02µF

0.1µF

MBR330p

MODE LOGIC

220pF

C2

D3

V

IN

LT1170

R4

V

SW

FB

V

C

Q1

R3

C3

High Efficiency 5V Buck Converter

C5

0.03µF

GND

DIODE

LT1432

V

IN

4.7µF

TANT

GND

C3

+

V

SW

LT1170

FB

V

C

R1 680Ω

C4

D1

V

C

V

IN

MODE

R6

330Ω

C4

R2*

L1

25µH

2000µF

10µH

3A

100µF

16V

C1

D1

T1

1

M

N

D2

D4

R5 1Ω

D2

1N4148

L1

50µH

0.013Ω

+

V

LIM

V

OUT

* R2 IS MADE FROM PC BOARD COPPER TRACES. ** MAXIMUM CURRENT IS DETERMINED BY THE CHOICE OF LT1070 FAMILY. SEE APPLICATION SECTION.

+

×

C2 390µF 16V

R1

3.74k

R2

1.24k

OPTIONAL OUTPUT FILTER

V

OUT

5V 3A**

1170/1/2 TA17

V

OUT

5V, 6A

1170/1/2 TA16

14

PACKAGE DESCRIPTIO

LT1170/LT1171/LT1172

U

Dimensions in inches (millimeters) unless otherwise noted.

J8 Package

8-Lead CERDIP (Narrow 0.300, Hermetic)

(LTC DWG # 05-08-1110)

CORNER LEADS OPTION

(4 PLCS)

0.023 – 0.045

(0.584 – 1.143)

HALF LEAD

0.045 – 0.068

(1.143 – 1.727)

FULL LEAD

OPTION

0.300 BSC

(0.762 BSC)

0.008 – 0.018

(0.203 – 0.457)

NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR TIN PLATE LEADS

0° – 15°

OPTION

0.005

(0.127)

MIN

0.025

(0.635)

RAD TYP

0.045 – 0.065

(1.143 – 1.651)

0.014 – 0.026

(0.360 – 0.660)

0.405

(10.287)

MAX

87

12

65

3

4

0.220 – 0.310

(5.588 – 7.874)

0.015 – 0.060

(0.381 – 1.524)

0.100

(2.54)

BSC

0.200

(5.080)

MAX

0.125

3.175 MIN

J8 1298

15

LT1170/LT1171/LT1172

PACKAGE DESCRIPTIO

0.320 – 0.350 (8.13 – 8.89)

0.420 – 0.480

(10.67 – 12.19)

0.760 – 0.775

(19.30 – 19.69)

U

Dimensions in inches (millimeters) unless otherwise noted.

K Package

4-Lead TO-3 Metal Can

(LTC DWG # 05-08-1311)

1.177 – 1.197

(29.90 – 30.40)

0.470 TP

0.060 – 0.135

(1.524 – 3.429)

0.038 – 0.043

(0.965 – 1.09)

18°

P.C.D.

72°

0.655 – 0.675

(16.64 – 19.05)

0.151 – 0.161 (3.84 – 4.09)

DIA 2 PLC

0.167 – 0.177 (4.24 – 4.49)

R

0.490 – 0.510

(12.45 – 12.95)

R

K4(TO-3) 1098

N8 Package

8-Lead PDIP (Narrow 0.300)

(LTC DWG # 05-08-1510)

876

0.255 ± 0.015* (6.477 ± 0.381)

12

0.300 – 0.325

(7.620 – 8.255)

0.065

(1.651)

0.009 – 0.015

(0.229 – 0.381)

+0.035

0.325

–0.015 +0.889

8.255

()

–0.381

*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)

TYP

0.045 – 0.065

(1.143 – 1.651)

0.100

(2.54)

BSC

0.400*

(10.160)

MAX

3

5

4

0.130 ± 0.005

(3.302 ± 0.127)

0.125

(3.175)

MIN

0.018 ± 0.003

(0.457 ± 0.076)

0.020

(0.508)

MIN

N8 1098

16

PACKAGE DESCRIPTIO

LT1170/LT1171/LT1172

U

Dimensions in inches (millimeters) unless otherwise noted.

Q Package

5-Lead Plastic DD Pak

(LTC DWG # 05-08-1461)

0.256

(6.502)

0.060

(1.524)

0.300

(7.620)

BOTTOM VIEW OF DD PAK

HATCHED AREA IS SOLDER PLATED

COPPER HEAT SINK

(1.524)

(1.905)

0.060

0.075

0.183

(4.648)

0.060

(1.524)

TYP

0.330 – 0.370

(8.382 – 9.398)

+0.012

0.143 –0.020

+0.305

3.632

()

–0.508

0.028 – 0.038

(0.711 – 0.965)

0.390 – 0.415

(9.906 – 10.541)

15

° TYP

0.067

(1.70)

BSC

S8 Package

8-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)

0.165 – 0.180

(4.191 – 4.572)

0.059

(1.499)

TYP

0.013 – 0.023

(0.330 – 0.584)

0.045 – 0.055

(1.143 – 1.397)

+0.008

0.004 –0.004

+0.203

0.102

()

–0.102

0.095 – 0.115

(2.413 – 2.921)

± 0.012

0.050

(1.270 ± 0.305)

Q(DD5) 1098

0.228 – 0.244

(5.791 – 6.197)

0.010 – 0.020

(0.254 – 0.508)

0.008 – 0.010

(0.203 – 0.254)

*

DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

**

DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

×

°

45

0.016 – 0.050

(0.406 – 1.270)

0°– 8° TYP

0.053 – 0.069

(1.346 – 1.752)

0.014 – 0.019

(0.355 – 0.483)

TYP

0.189 – 0.197* (4.801 – 5.004)

7

8

1

2

5

6

0.150 – 0.157** (3.810 – 3.988)

3

4

0.004 – 0.010

(0.101 – 0.254)

0.050

(1.270)

BSC

SO8 1298

17

LT1170/LT1171/LT1172

PACKAGE DESCRIPTIO

U

Dimensions in inches (millimeters) unless otherwise noted.

SW Package

16-Lead Plastic Small Outline (Wide 0.300)

(LTC DWG # 05-08-1620)

0.398 – 0.413*

(10.109 – 10.490)

15 14

16

12

13

10 9

11

NOTE 1

2345

0.050

(1.270)

BSC

1

0.014 – 0.019

(0.356 – 0.482)

TYP

0.291 – 0.299** (7.391 – 7.595)

0.010 – 0.029

(0.254 – 0.737)

0.009 – 0.013

(0.229 – 0.330)

NOTE:

1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS. THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS

DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

*

DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

**

NOTE 1

× 45°

0.016 – 0.050

(0.406 – 1.270)

° – 8° TYP

0

0.093 – 0.104

(2.362 – 2.642)

6

78

0.037 – 0.045

(0.940 – 1.143)

0.394 – 0.419

(10.007 – 10.643)

0.004 – 0.012

(0.102 – 0.305)

S16 (WIDE) 1098

18

PACKAGE DESCRIPTIO

LT1170/LT1171/LT1172

U

Dimensions in inches (millimeters) unless otherwise noted.

T Package

5-Lead Plastic TO-220 (Standard)

(LTC DWG # 05-08-1421)

0.390 – 0.415

(9.906 – 10.541)

0.460 – 0.500

(11.684 – 12.700)

0.067

BSC

(1.70)

0.147 – 0.155

(3.734 – 3.937)

0.230 – 0.270

(5.842 – 6.858)

0.330 – 0.370

(8.382 – 9.398)

0.028 – 0.038

(0.711 – 0.965)

DIA

0.570 – 0.620

(14.478 – 15.748)

SEATING PLANE

0.260 – 0.320 (6.60 – 8.13)

0.700 – 0.728

(17.78 – 18.491)

0.152 – 0.202

(3.861 – 5.131)

0.135 – 0.165

(3.429 – 4.191)

0.165 – 0.180

(4.191 – 4.572)

0.620

(15.75)

TYP

0.045 – 0.055

(1.143 – 1.397)

0.095 – 0.115

(2.413 – 2.921)

0.155 – 0.195*

(3.937 – 4.953)

0.013 – 0.023

(0.330 – 0.584)

* MEASURED AT THE SEATING PLANE

T5 (TO-220) 0399

I

nformation furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

19

LT1170/LT1171/LT1172

A

TYPICAL APPLICATIO

V

IN

28V

GND

+

C5*

100µF

U

Positive Current Boosted Buck Converter

V

IN

LT1170

470Ω 2W

D2

V

SW

R7

FB

V

C

R3 680Ω

C1

0.33µF

1k

C4

0.01µF

6

C3

0.47µF

0.002µF

V

LM308

4

200pF

R6 470Ω

C6

1: N

R2

1.24k

IN

7

–

+

8

1.24k

N ≈ 0.25

D1

2

R5

5k

3

R4

V

OUT

R1

+

5k

5V, 10

C2 5000µF

* REQUIRED IF INPUT LEADS ≥ 2"

1170/1/2 TA18

RELATED PARTS

PART NUMBER DESCRIPTION COMMENTS

LT1070/LT1071/LT1072 5A/2.5A/1.25A High Efficiency Switching Regulators 40kHz, VIN to 60V, VSW to 75V LT1074/LT1076 5.5A/2A Step-Down Switching Regulators 100kHz, Also for Positive-to-Negative Conversion LT1082 1A, High Voltage, High Efficiency Switching Regulator VIN to 75V, VSW to 100V, Telecom LT1268/LT1268B 7.5A, 150kHz Switching Regulators VIN to 30V, VSW to 60V LT1269/LT1271 4A High Efficiency Switching Regulators 100kHz/60kHz, VIN to 30V, VSW to 60V LT1270/LT1270A 8A and 10A High Efficiency Switching Regulators 60kHz, VIN to 30V, VSW to 60V LT1370 500kHz High Efficiency 6A Switching Regulator High Power Boost, Flyback, SEPIC LT1371 500kHz High Efficiency 3A Switching Regulator Good for Boost, Flyback, Inverting, SEPIC LT1372/LT1377 500kHz and 1MHz High Efficiency 1.5A Switching Regulators Directly Regulates ±V LT1373 250kHz Low Supply Current High Efficiency 1.5A Switching Regulator Low 1mA Quiescent Current LT1374 4A, 500kHz Step-Down Switching Regulator Synchronizable, VIN to 25V LT1375/LT1376 1.5A, 500kHz Step-Down Switching Regulators Up to 1.25A Out from an SO-8 LT1425 Isolated Flyback Switching Regulator 6W Output, ±5% Regulation,

No Optocoupler Needed

LT1507 500kHz Monolithic Buck Mode Switching Regulator 1.5A Switch, Good for 5V to 3.3V LT1533 Ultralow Noise 1A Switching Regulator Push-Pull, <100µV

OUT

Output Noise

P-P

20

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417 ● (408) 432-1900 FAX: (408) 434-0507

●

TELEX: 499-3977 ● www.linear-tech.com

117012fe LT/TP 1299 2K REV E • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 1991

Datasheet LT1172, LT1171, LT1170 Datasheet (Linear Technology)

Specifications and Main Features

Frequently Asked Questions

User Manual